1SSL_CTX_SET_CERT_VERIFY_CALLBACK(3) OpenSSLSSL_CTX_SET_CERT_VERIFY_CALLBACK(3)
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NAME

6       SSL_CTX_set_cert_verify_callback - set peer certificate verification
7       procedure
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SYNOPSIS

10        #include <openssl/ssl.h>
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12        void SSL_CTX_set_cert_verify_callback(SSL_CTX *ctx,
13                                              int (*callback)(X509_STORE_CTX *, void *),
14                                              void *arg);
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DESCRIPTION

17       SSL_CTX_set_cert_verify_callback() sets the verification callback
18       function for ctx. SSL objects that are created from ctx inherit the
19       setting valid at the time when SSL_new(3) is called.
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NOTES

22       Whenever a certificate is verified during a SSL/TLS handshake, a
23       verification function is called. If the application does not explicitly
24       specify a verification callback function, the built-in verification
25       function is used.  If a verification callback callback is specified via
26       SSL_CTX_set_cert_verify_callback(), the supplied callback function is
27       called instead. By setting callback to NULL, the default behaviour is
28       restored.
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30       When the verification must be performed, callback will be called with
31       the arguments callback(X509_STORE_CTX *x509_store_ctx, void *arg). The
32       argument arg is specified by the application when setting callback.
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34       callback should return 1 to indicate verification success and 0 to
35       indicate verification failure. If SSL_VERIFY_PEER is set and callback
36       returns 0, the handshake will fail. As the verification procedure may
37       allow the connection to continue in the case of failure (by always
38       returning 1) the verification result must be set in any case using the
39       error member of x509_store_ctx so that the calling application will be
40       informed about the detailed result of the verification procedure!
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42       Within x509_store_ctx, callback has access to the verify_callback
43       function set using SSL_CTX_set_verify(3).
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RETURN VALUES

46       SSL_CTX_set_cert_verify_callback() does not return a value.
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WARNINGS

49       Do not mix the verification callback described in this function with
50       the verify_callback function called during the verification process.
51       The latter is set using the SSL_CTX_set_verify(3) family of functions.
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53       Providing a complete verification procedure including certificate
54       purpose settings etc is a complex task. The built-in procedure is quite
55       powerful and in most cases it should be sufficient to modify its
56       behaviour using the verify_callback function.
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BUGS

59       SSL_CTX_set_cert_verify_callback() does not provide diagnostic
60       information.
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SEE ALSO

63       ssl(7), SSL_CTX_set_verify(3), SSL_get_verify_result(3),
64       SSL_CTX_load_verify_locations(3)
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67       Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved.
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69       Licensed under the OpenSSL license (the "License").  You may not use
70       this file except in compliance with the License.  You can obtain a copy
71       in the file LICENSE in the source distribution or at
72       <https://www.openssl.org/source/license.html>.
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761.1.1                             2018-09-11SSL_CTX_SET_CERT_VERIFY_CALLBACK(3)
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